The present invention relates a reciprocating motor, and more particularly, to an improved reciprocating motor in which the width of an entrance of an opening where a winding coil is positioned, that is, the interpole distance is minimized, the space of the opening is maximized to reduce the amount of a pricy permanent magnet to be used, its output is heightened and its structure is simplified to be compact.
Generally, a motor is an instrument for converting an electric energy to a kinetic energy. There are two types of motors: one is a rotary motor which converts the electric energy to a rotational movement, and the other is a reciprocating motor which converts the electric energy to a linear reciprocal movement.
As a driving source, the motor is adopted for use to various fields. Especially, it is installed in almost every home appliance such as a refrigerator, an air conditioner, a washing machine or an electric fan. In case of the refrigerator and the air conditioner, the motor is not only used to rotate a ventilating fan, but also installed as a driving source at a compressor of a cooling cycle apparatus of the refrigerator and the air conditioner.
FIG. 1 is a drawing illustrating an example of a reciprocating motor in accordance with a conventional art.
As shown in FIG. 1, the reciprocating motor includes a cylindrical outer core 10 formed having a predetermined width and length, a cylindrical inner core 20 inserted in the outer core 10 with a predetermined space, a winding coil 30 coupled to the outer core 10 or the inner core 20, and a mover 40 movably inserted between the outer core 10 and the inner core 20.
FIG. 1 shows the structure that, the winding coil 30 is coupled to the outer core 10.
The outer core 10 has a xe2x80x98Uxe2x80x99-shaped section with a predetermined thickness, so that an opening 11 is formed in which the winding coil 30 is positioned. The xe2x80x98Uxe2x80x99-shaped outer core 10 forms a pass part 12 at which a flux flows, and a pole part 13 is formed at both ends of the pass part 12.
The inner core 20 has a section with a length corresponding to that of the outer core 10 and a predetermined width.
The outer core 10 and the inner core 20 are fixed at a separate frame (not shown) to constitute a stator (S).
The mover 40 includes a cylindrical magnet holder 41 inserted between the outer core 10 and the inner core 20 and a plurality of permanent magnets 42 combined at the outer circumferential surface of the magnet holder 41.
The operation of the reciprocating motor constructed as described above will now be explained.
FIG. 2 is a sectional view showing an operational state of the general reciprocating motor.
As shown in FIG. 2, first, when a current flows to the winding coil 30, a flux is formed around the winding coil 30 due to the current flowing along the winding coil 30. The flux flows to form a closed loop along the pass part 12 of the outer core and the inner core 20 which constitute the stator (S).
The interaction between the flux according to the current flowing along the coil 30 and the flux according to the permanent magnet 42 constituting the mover 40 makes the permanent magnet 42 to move in the axial direction.
When the direction of the current flowing to the winding coil 30 is changed, the direction of the flux formed at the pass part 12 of the outer core and the inner core 20 is accordingly changed, and thus, the permanent magnet 42 is moved in the opposite direction.
When the current is supplied to the permanent magnet 42 by changing its direction by turns, the permanent magnet 42 is moved linearly and reciprocally between the outer core 10 and the inner core 20. Accordingly, the mover 40 has a linear reciprocal driving force.
In the reciprocating motor, the length Lm of the permanent magnet 42 of the mover 40 is usually equivalent to the sum of the length Lp of the pole part and the interpole distance Lb.
Accordingly, since the length of the permanent magnet 42 is in proportion to the interpole distance Lb positioned at both sides of the opening 11, the shorter the interpole distance Lb is, the shorter Lm of the permanent magnet 42 becomes.
The length Lp of the pole part corresponds to the stroke, and the interpole distance Lb is equivalent to the width of the entrance of the opening 11.
The permanent magnet 42 of the mover 40 of the reciprocating motor costs much for its materials. Thus, in order to incur a less production cost, its amount to be used should be reduced. Especially, in case of a mass production, it is requisite to reduce a production unit cost.
In addition, in a case that the reciprocating motor is mounted in a different system, in order to occupy a less installation space, the reciprocating motor needs to be compact structurally.
Thus, it is critical to reduce the length of the high-priced permanent magnet 42 by reducing the interpole distance Lb to thereby reduce the cost of materials, prevent leakage of the magnetic flux and have a compact structure while obtaining the inner space of the opening as large as possible where the winding coil 30 is positioned.
In consideration of this, a structure as shown in FIG. 3 has been proposed.
FIG. 3 is a sectional view of a reciprocating motor proposed during a research and development of the inventor of the present invention.
With reference to FIG. 3, the structure includes a xe2x80x98Uxe2x80x99-shaped pass part 12, of the outer core 10 where the winding coil 30 is positioned, having a section with a predetermined thickness; a triangular extended part 14 protrusively extended in a triangle form at inner sides of both ends of the pass part 12, and a pole part 15 formed by the both ends of the pass part 12 and the triangular extended part 14.
An opening 16 where the winding coil 30 is positioned is formed by the inner side of the pass part 12 and the inner side of the triangular extended part 14. The distance between the inner ends of the triangular extended parts 14, that is, the interpole distance Lbxe2x80x2 between the pole parts 15, forms the entrance of the opening 16.
However, with such a structure, if the triangular extended part 14 is enlarged to reduce the width of the entrance of the opening 16 in which the winding coil 30 is positioned, the inner space of the opening 16 becomes small, causing that the number of winding of the winding coil is reduced. On the other hand, if the triangular extended part 14 is made small to enlarge the inner space of the opening 16, the entrance of the opening 16 is widened, causing increase in the amount of the permanent magnet to be used.
Meanwhile, if the triangular extended part 14 is sharpened to maintain the inner space of the opening 16 and shorten the length of the entrance of the opening 16, that is, if the angle made as the inner face of the pass part 12 and the inner face of the triangular extended part 14 meet is almost perpendicular, the flow resistance of the flux flowing to the outer core 10 is rapidly increased, causing a damage to the flux.
In addition, with such a structure, when the mover 40 including the permanent magnet 42 is being linearly and reciprocally moved, the range in which the end portion of the mover 40 is protruded outwardly of the pole part 15 becomes wide. Thus, the space between the mover and other components should be distanced, causing a problem that its structure is enlarged.
Therefore, an object of the present invention is to provide a reciprocating motor in which the width of an entrance of an opening where a winding coil is positioned, that is, the interpole distance is minimized, the space of the opening is maximized to reduce an amount of a pricy permanent magnet to be used, its output is heightened and its structure is simplified to be compact.
In order to achieve the above objects, there is provided a reciprocating motor having an outer core, inner cores inserted at a predetermined distance from the outer core, a winding coil inserted into the outer core or the inner core and a mover provided with a permanent magnet and inserted to be linearly movable between the outer core and the inner core, including: a ring-shaped opening of which one side is opened so as for the winding coil to be positioned inside the core; a first step portion extendedly formed at the inner face of the opening such that the interval inside the opening becomes narrow as it comes to the entrance; and a second step portion having a predetermined width and length extendedly formed from the first step portion.